Convert an AWS secret access key to an SES SMTP password using Ruby (https://docs.aws.amazon.com/ses/latest/dg/smtp-credentials.html)

aws-ses-convert-credentials.rb

#!/usr/bin/ruby

require 'openssl'
require 'base64'

# Define a method to calculate HMAC SHA-256
def hmac_sha256(key, data)
  OpenSSL::HMAC.digest('sha256', key, data)
end

# Define a method to generate the SMTP password
def generate_smtp_password(key, region)
  # Fixed values
  date = '11111111'
  service = 'ses'
  terminal = 'aws4_request'
  message = 'SendRawEmail'
  version = 0x04

  # Perform the HMAC SHA-256 operations
  k_date = hmac_sha256('AWS4' + key, date)
  k_region = hmac_sha256(k_date, region)
  k_service = hmac_sha256(k_region, service)
  k_terminal = hmac_sha256(k_service, terminal)
  k_message = hmac_sha256(k_terminal, message)

  # Concatenate the version and the k_message
  signature_and_version = [version].pack('C') + k_message

  # Encode the result in Base64 to get the SMTP password
  Base64.strict_encode64(signature_and_version)
end

# Accept key and region as command-line arguments
if ARGV.length != 2
  puts 'Usage: ruby script.rb <AWS_SECRET_ACCESS_KEY> <AWS_REGION>'
  exit
end

key = ARGV[0]
region = ARGV[1]

smtp_password = generate_smtp_password(key, region)
puts "SMTP Password: #{smtp_password}"